共查询到20条相似文献,搜索用时 453 毫秒
1.
T. Kawahara M. Miyazaki A. Kimura Y. Okamoto J. Morimoto T. Miyakawa 《Applied Physics A: Materials Science & Processing》1999,69(3):343-346
The noncontact imaging of the buried structures is carried out in the open-air atmosphere by using the photothermal deflection
(PTD) method. We applied these techniques to the layered samples. Besides the PTD images for the optically opaque buried structures,
the parameters of the materials such as thermal diffusivity can also be calculated from the PTD amplitude and phase signal
in the PTD scanning images. When the PTD signals at two different modulation frequencies are used, the thermal diffusivity
of the buried structure can be obtained from the PTD signal outside of the sample nondestructively.
Received: 27 November 1998 / Accepted: 18 March 1999 / Published online: 7 July 1999 相似文献
2.
A distance-scan method to determine the distance between the probe beam and sample, which is not easily measured exactly, in photothermal deflection (PD) was reported, with which the distance and thermal diffusivity of the deflecting medium can be simultaneously measured. Probe beam size effect (PBSE) on PD phase signal was quantitatively analyzed to clearly show its physical meaning. The measured distance was experimentally verified as correct and reliable, and the measured thermal diffusivities of N2 and CO2 are in good agreement with the literature values. They could not be precisely measured by phase signal without considering the PBSE. 相似文献
3.
Study on thermal diffusivity of materials by laser photothermal reflection technique 总被引:1,自引:0,他引:1
A method of measuring thermal diffusivity of materials at room temperature by photothermal reflection technique is described. An intensity-modulated Ar+ laser beam is used as incident light. The beam is focused to about 1 mm diameter spot and illuminates the sample surface. HgCdTe infrared detector is used to receive photothermal signal. Using this technique, the photothermal signals are experimentally measured as the function of different frequencies. The thermal diffusivities can be obtained by fitting the experimental data. On the other hand, the thermal diffusivities of one-way composite and orthogonal symmetric arranged composites Al2O3/Al are measured in transverse, longitudinal and arbitrary directions. The results show that the diffusivity of one-way material decreases with the increase of the measurement angle; the diffusivity of orthogonally arranged material almost keeps the same when measurement angle changes. 相似文献
4.
The thermal diffusivity h of a thin film on a substrate is measured by using the mirage technique. The photothermal deflection of the probe beam is caused by the heat field and the substrate, heated by the pump beam. From the experimental data a two-dimensional algorithm is proposed to obtain the measurements of the diffusivity of film and substrate in one set of mirage detection. 相似文献
5.
S. I. Yun Ki-Dong Oh Kwon-Sang Ryu Chang-Geon Kim H. L. Park H. J. Seo Chae Kum 《Applied physics. B, Lasers and optics》1986,40(2):95-98
We have used a modified photothermal probe beam deflection system with a back pumping configuration for the measurements of the temperature-dependent thermal diffusivity of atmospheric air. The results are consistent and reasonably well agree with the literature values. The measured thermal diffusivity values are the same for the same measuring temperature regardless of the beam offsets and the deflecting surface temperatures. For the gas with known temperature-dependent thermal diffusivity, this method can be used to deduce the temperature of a gas from the measured thermal diffusivity value. 相似文献
6.
Drawing on interferometry and Fourier analysis, this paper describes the use of a two-beam thermal lens technique for measuring thermo-optical properties in optical materials. The procedure consists of yield interference patterns deformed by a localized photothermal effect. The photothermal phase shift is locally induced by the pump beam focused on a tested sample located on an on-axis probe beam, which is the first arm of a Mach-Zehnder interferometer. The plane where the effect is localized is imaged onto a CCD camera. Then two interferograms are recorded: one without effect and the other one with the induced photothermal phase. Fourier analysis performed on these interferograms allow us to plot the thermal lens map and, therefore, to estimate thermo-optic constant of Malachite Green in water solution. The method is applied to measure low linear absorptions of a diluted sample of Rhodamine B in water solution at 633 nm, showing that the proposed technique allows to measure photothermal phase shift as low as 3.1 mrad at 8 mW of input power in diluted materials. 相似文献
7.
调制激光作用牙齿组织发生散射形成光子密度波, 而由于光热效应产生热波, 基于一维介质辐射传输漫射近似方程与一维热传导方程建立了调制激光作用牙齿组织半透明混合介质的一维热波数学模型. 利用该模型仿真分析了牙齿龋损特性参数(牙釉质龋损层光吸收系数、散射系数、热扩散系数及龋损深度)对光热辐射动态响应特性的影响与规律. 利用红外探测器(HgCdTe, 2–12 μm)记录808 nm半导体激光激发牙齿组织产生的热波信号, 由锁相放大器计算热波信号的幅值与相位. 通过频率扫描试验获得了牙齿组织的光热动态响应, 利用多参数最佳统计拟合方法得到了牙齿组织特性参数. 结果表明光热辐射测量对牙齿组织不均匀性和龋损特性均具有较高敏感性与特异性. 相似文献
8.
J. Rantala J. Jaarinen P. K. Kuo 《Applied Physics A: Materials Science & Processing》1992,55(6):586-595
Computer simulations have been carried out to study the effects of the experimental parameters when the mirage method has been applied to thermal diffusivity measurements of oriented polymer films. The parameters under study are the thermal diffusivity of the fluid surrounding the sample, the modulation frequency and the radius of the heating beam, the height and the radius of the probe beam, and the sample thickness and thermal diffusivity. Proposals for the optimum parameter values to maximize the measurement sensitivity for the sample diffusivity are made and the difficulties arising from the low diffusivity of the samples are described. It is also concluded that because the thermal properties of the fluid surrounding the sample have a strong contribution to the mirage signals, the signals do not include any simple feature corresponding to the sample diffusivity. Therefore it should be determined from the entire measurement data using regression methods. 相似文献
9.
J. Bodzenta J. Mazur A. Ka?mierczak-Ba?ata 《Applied physics. B, Lasers and optics》2011,105(3):623-630
The thermal diffusivity and the thermal conductivity of compressed expanded graphite (CEG) samples were investigated by photothermal
measurements in two geometries differing by a place of temperature disturbance detection. This disturbance can be detected
on a surface opposite to the one at which the disturbance was generated (rear detection) or on the same surface (front detection).
A measurement based on the rear detection allowed us to determine the effective thermal diffusivity of the sample, while the
method with front detection gives the possibility of analysis of homogeneity of the sample. It is shown that the thermal diffusivity
of CEG strongly depends on its apparent density. Moreover, CEG samples reveal anisotropy of the thermal properties. The thermal
diffusivity in the direction parallel to the compacting axis is lower than the one in the direction perpendicular to it. The
parallel thermal diffusivity decreases with growing apparent density, while the perpendicular thermal diffusivity significantly
grows when the apparent density grows. The perpendicular thermal conductivity exhibits the same behavior as the perpendicular
thermal diffusivity. The parallel thermal conductivity slightly grows with growing density and then reaches a plateau. The
anisotropy of CEG samples grows with growing apparent density and vanishes for low-density samples. The photothermal measurement
with front signal detection revealed that the CEG samples are non-homogeneous in the direction of the compacting axis and
can be modeled by a two-layer system. 相似文献
10.
11.
Z. J. Chen J. W. Fang S. Y. Zhang 《The European physical journal. Special topics》2008,153(1):195-198
For a film-on-substrate system, in the case of thin films
with lower thermal diffusivities compared to substrates, the phase
characterization of the photothermal signals is analyzed. Moreover, the
numerical estimations of multiparameter are performed, which show the
feasibility of simultaneous determination of the thermal diffusivities of
the film and the substrate, as well as the thermal interface resistance of
the film/substrate. Because the thermal diffusivity of the thin-film and the
thermal interface resistance may be highly correlated, a genetic algorithm
is used as an estimation method for the determination of the thermal
properties of thin films with low thermal diffusivity. 相似文献
12.
Jerzy?Bodzenta Anna?Ka?mierczak-Ba?ata Jacek?Mazur 《Central European Journal of Physics》2010,8(2):207-220
Information on the thermal properties of materials is very important both in fundamental physical research and in engineering
applications. The development of materials with desirable heat transport properties requires methods for their experimental
determination. In this paper basic concepts of the measurement of parameters describing the heat transport in solids are discussed.
Attention is paid to methods utilizing nonstationary temperature fields, especially to photothermal methods in which the temperature
disturbance in the investigated sample is generated through light absorption. Exemplary photothermal measuring techniques,
which can be realized using common experimental equipment, are described in detail. It is shown that using these techniques
it is possible to determine the thermal diffusivity of bulk transparent samples, opaque and semi-transparent plate-form samples,
and the thermal conductivity of thin films deposited on thick substrates. Results of the investigation of thermal diffusivity
of the ground in the polar region, which is based on the analysis of the propagation of the thermal wave generated by sun-light,
are also presented. Based on chosen examples one can state that photothermal techniques can be used for determination of the
thermal properties of very different materials. 相似文献
13.
In this paper we present results of noncontact measurements of the thermal diffusivity of infrared semi-transparent n-CdMgSe mixed semiconductor crystals by means of the photothermal radiometry (PTR) in a transmission configuration. In order to overcome an influence of the infrared semi-transparency and plasma waves on the PTR signal from n-CdMgSe mixed crystals the samples were covered by thin aluminum foils on both sides. The thermal diffusivities of n-CdMgSe mixed crystals were estimated from PTR phase frequency characteristics using a well-known formula. It was found that the obtained results are underestimated in comparison to thermal diffusivities estimated from the PPE (photopyro-electric) measurements. A three layer model of a PTR signal was applied in order to estimate an error in determination of the thermal diffusivity of a sample caused by aluminum foils. 相似文献
14.
XIAO Liantuan LI Changyong ZHANG Linjie ZHAO Yanting JIA Suotang ZHOU Guosheng 《Chinese Journal of Lasers》2000,9(6):538-544
1 Introduction Thermaldiffusivitymeasurementisparticularlyimportantformaterialsofnewconceptioninordertocontroltheirmanufacturingprocess .Atthesametime ,thedeterminationofliquidthermaldiffusivityisalsoimportantwhentheliquidisusedasacoolantforhigh powera… 相似文献
15.
Xiao Liantuan Li Changyong Zhang Linjie Zhao Yanting Jia Suotang Zhou Guosheng 《中国光学快报(英文版)》2000,9(6)
The pulsed-laser pumped photothermal deflection spectroscopy (PPDS) is applied to measure liquid thermal diffusivity in a modified collinear configuration. Here the pulsed beam is regarded as in the form of a Dirac delta function. The experiment setup used is described. Measurement result for the thermal diffusivity of a liquid sample(magnta/ethanol saturated solution) is reported. The measurement error is less than 3%. 相似文献
16.
17.
I. Rejeena B. Lillibai V. Thomas V. P. N. Nampoori P. Radhakrishnan 《Journal of fluorescence》2016,26(4):1161-1165
In the present paper, the investigations on the non radiative decay mechanism, optical band gap determination from absorption spectroscopic studies and fluorescence emission by photo luminescence techniques using different excitation wavelengths on gel derived lead di bromide single crystals are reported. Non radiative decay of the sample is studied using high sensitive dual beam mode matched thermal lens technique. For the thermal lensing experiment the crystal in solution phase is incorporated with rhodamine 6G dye for enhancing the absorption of the crystal sample. The thermal diffusivity of lead di bromide is determined using the probe beam intensity v/s time measurements. 相似文献
18.
Thermoreflectance and photodeflection combined for microscopic characterization of metallic surfaces
A non-contact technique is presented that provides information on thermal diffusivity at the cubic micron scale in metal surfaces.
It relies on the simultaneous fit of the frequency dependence of two mechanisms that appear when heating the surface of the
sample with a modulated laser beam, the thermoreflectance (change in reflectivity with temperature) and photodeflection (the
deflection of the beam due to the surface deformation). A complete analytical model is presented that takes both mechanisms
into account, showing that the relative importance of both mechanisms depends strongly on the material under test and varies
in several orders of magnitude between different metallic alloys. By filtering the reflected signal with an adjustable knife
edge, the photodeflection signal can be enhanced. It is also shown how the signal arising from each mechanism depends strongly
on the relative position of the pump and probe beams. A characteristic modulating frequency appears at which a drop in the
signal with frequency is observed that is coincident for both mechanisms. From the determination of the characteristic frequency,
the local heat diffusivity can be determined as it is shown for the case of an AISI304 stainless steel sample.
PACS 78.20.Nv; 65.40.-b; 72.15.Eb 相似文献
19.
S. Ktifa A. Souissi F. Saadallah V. Sallet M. Oueslati N. Yacoubi 《Applied Physics A: Materials Science & Processing》2014,114(2):559-563
ZnO thin films were grown by metal-organic chemical vapor deposition on Zn- and O-polar surfaces of ZnO substrate. The effect of Zn- and O-polar substrate on the surface morphology and opto-thermal proprieties has been studied. Hall-measurements were used to determine the carrier concentration of the deposited films. Photothermal deflection spectroscopy (PDS) was used to determine the optical absorption spectrum and the gap energy by comparing experimental amplitude of the photothermal signal to the corresponding theoretical one. Thermal conductivity and diffusivity were also deduced from the photothermal deflection measurements. The found values were very low due to the thermal resistivity of the layer–substrate interface. 相似文献